Device and method for controlling a cooling air flow of a gas turbine

ABSTRACT

An apparatus for controlling a cooling air flow, in particular a gas turbine cooling air flow, is for the control, specific to requirement, of a cooling air flow using low-maintenance. A control fluid flow is introduced into the cooling air flow in the region of the flow duct with a flow component transverse to the flow direction of the cooling air flow through the flow duct. As such, the flow rate of the cooling air flow is adjustable as a function of control parameters of the control fluid flow and/or other parameters.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/EP00/07255 which has an Internationalfiling date of Jul. 27, 2000, which designated the United States ofAmerica, the entire contents of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The invention generally relates to a gas turbine and method forcontrolling cooling of a gas turbine.

BACKGROUND OF THE INVENTION

An air-cooled gas turbine blade appliance is known from EP 0 768 448 A1.The rotor blades are inserted on rotatable carrier disks. Due to the hotair supplied for the operation of the gas turbine, temperature-sensitiveregions of the gas turbine are also heated and can be subjected todamage by this. The rotor blades, which are inserted on the rotatablecarrier disks driven by the hot air, are cooled by cooling air suppliedfrom the carrier disk. For cooling purposes, cooling air suppliedradially from the outside flows through the stationary guide blades.This is used, inter alia, for cooling carrier disk lateral spaceslocated between the rotor blades and the guide blades.

For feeding the cooling air to the carrier disk lateral spaces at theradially inner end of a guide blade, the guide blade has an openingthrough which the cooling air, which is led through an external coolingair supply duct, is fed. The discharge of the rest of the cooling airtakes place, essentially, through a large number of small openings,so-called film cooling holes, in a so-called blade nose into the hot airflow, so that a cooling air film is formed on the outside of the gasturbine blade.

In the case of an unrestricted cooling air supply with the objective ofmaximum cooling, the efficiency of the gas turbine, which is essentiallydetermined by the temperature of the hot gas introduced, is greatlyreduced by the large quantities of cooling air supplied and the energyconsumption of the gas turbine is essentially increased.

Control valves are inserted to combat this. In general, these arecommercial valve shapes and are located radially outside on the guideblade or further upstream in the supply path of the cooling air, in thecooling air supply duct.

Although, on the one hand, this makes the valve easily accessible inorder, for example, to carry out possible repairs or adjustments, itmeans, on the other hand, that only a simultaneous adjustment ispossible of the pressure of the cooling air for the carrier disk lateralspace and of the pressure of the cooling air which flows through thefilm cooling holes onto the blade nose. Where adjustment takes place toa very low cooling air pressure, this can easily lead to break-down ofthe cooling air film on the blade nose and, in consequence, there is nolonger adequate cooling of the guide blade surface. If, on the otherhand, the cooling air pressure is adjusted to be strong to produce anadequate cooling film, a powerful cooling air flow is produced in thehot air and this leads to a reduction in the power of the gas turbineand a high consumption of energy.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a control of a coolingair flow. In the case of a gas turbine, in particular, an automatic gasturbine, adequate cooling of the carrier disk lateral space by a supplyof cooling air should be reliably ensured independently of the operatingconditions. Further, at the same time, a high gas turbine efficiencyshould be achieved.

This object is achieved by providing an appliance for controlling a gasturbine cooling air flow through a flow duct. In one embodiment, itincludes, a control fluid flow which is introduced into the cooling airflow, in the region of the flow duct, with a flow component transverseto the flow direction of the cooling air flow through the flow duct. Inone embodiment, it is possible to adjust the flow rate of the coolingair flow as a function of control parameters of the control fluid flowand/or by the introduction geometry of the control fluid flow into thecooling air flow and/or by the geometry of the flow duct.

This type of control is well suited for difficult access locations onmachines or the like, which are also subjected to severe loads. Theappliance operates almost independently of dirt or other environmentalinfluences such as, for example, aggressive chemical attacks due to acorresponding cooling air flow. The control element is not subject toany wear and erosion-free switching is possible because of thecontactless adjustment without, for example, electrical current ormechanical appliances. Such a control appliance therefore requires verylittle maintenance because the control of the cooling air flow takesplace exclusively by way of a specially adjusted supply of a controlfluid flow. In the case of a failure of the control system, theoriginally adjusted cooling air flow takes place at its basic setting inany event. Independently of the function of the control flow, thecooling air flow can be adjusted before the appliance is put intooperation in such a way that it is sufficient for the desired function.

The control fluid flow intervenes in the flow behavior of the coolingair in such a way that it either accelerates or retards the flow,respectively increasing or lowering the flow rate. This essentiallytakes place by changes in the type of the active fluid flow in specifiedboundary or central regions of the cooling air flow in the flow duct.This is, in particular, also directed toward converting the flow from alaminar flow to a turbulent flow. The precondition is that the controlfluid flow should have a flow component suitable for influencing theflow when flowing into the cooling air flow. This refers to a componentof its main flow direction which is directed transverse to the flowdirection of the cooling air flow through the flow duct. By this, theflow behavior of the cooling air flow is influenced in a predeterminedmanner.

The control fluid is advantageously air. It is also conceivable tosupply to the active fluid a control fluid with a composition which is,to a certain extent, “neutral” with respect to the cooling air flow,such as an aqueous solution water.

The control fluid flow can, on the one hand, be adjusted in strength, orin its flow rate, and exerts, by this, a control influence on thecooling air flow. On the other hand, its introduction geometry, forexample the angular position of the control fluid flow relative to thecooling air flow, or the arrangement of the control fluid flow relativeto the cooling air flow, can be changed. Influence can also be effectedby changing the geometry of the flow duct through which the cooling airflows. The possibilities mentioned for the control can be combined withone another, the flow rate or strength of the control fluid flow beingadjusted after the installation of an appliance according to theinvention in a machine. In the case of a fixed geometry, the controlfluid flow is controlled by means of control parameters of the controlfluid flow which, however, depend on the respectively selected geometry.

The flow rate of the cooling air flow can preferably be adjusted byadjusting the pressure of the control fluid flow. Stepless and veryaccurate adjustment of the control fluid flow can be achieved by this,which adjustment can be undertaken with little complexity. Thisappliance also requires very little maintenance because a control flowis flowing almost continuously so that the supply ducts of the controlflow are kept free.

The flow rate of the control fluid is preferably small relative to theflow rate of the cooling air flow because, in this way, no changes areundertaken to the physical and chemical properties of the cooling airflow, for example pressure or temperature changes or changes to thechemical composition or to a cooling function. In the event of a failureof the control fluid flow, furthermore, the cooling air flow continuesto be sufficient to satisfy the envisaged duties so that the system, inwhich the appliance is inserted for control purposes, is not subject toany essential disturbance due to the failure of the control system. Theproportion of the control fluid flow which is introduced into thecooling air flow is, in total, preferably smaller than 50% and, inparticular, smaller than 10% of the total flow. The overall flowresulting, which is composed of the control fluid flow and the coolingfluid flow, practically corresponds to the previously introduced coolingair flow.

A further advantage of the control of a large flow by a small flow is,in addition, the low energy usage which is necessary for this purpose,or the small consumption of control fluid flow.

In a special introduction geometry, the control fluid flow can beintroduced radially into the cooling air flow in the flow duct, i.e. thecontrol fluid flow is located centrally and at right angles, or at leastwith a flow component at right angles, to the flow duct. This achieves anon-uniform incident flow of cooling air. In this way, the flow isstrongly swirled, the vortex strength depending on the controlparameters of the control fluid flow. In this way, the cooling air flowrate is reduced more or less strongly. Given optimum adjustment of theintroduction geometry and optimum control parameter values, the massflow becomes minimal. Given specified introduction geometry, acontinuous control of the cooling air flow from the normal value down toa minimum value can be undertaken by changing the control pressure.

In the case of different introduction geometry, the control fluid flowcan be introduced in the manner of a secant into the cooling air flowthrough the flow duct, i.e. although the control flow continues to belocated with at least a component at right angles to the cooling airflow direction, it is not arranged centrally, i.e. not at the maximumdiameter of the flow duct, in the case of a cylindrical flow duct, butmore or less laterally distant from it. Thus, the control fluid flow isintroduced into the cooling air flow corresponding to a type of secantin the case of a cylindrical flow duct. This type of designation shouldnot, however, be understood as a limitation to cylindrical flow ductsbut can also be applied to other duct shapes. This special type ofsupply generates a swirl in the flow duct and, in particular, in theactive fluid flow. This swirl stabilizes the cooling air flow andincreases its flow rate. Depending on the control parameters of thecontrol fluid flow, the flow rate correspondingly extends from thatoriginally adjusted to a maximum value. The achievable values of theflow rate also depend greatly on the introduction geometry of thecontrol fluid flow and the geometry of the flow duct in the case of boththe tangential and the radial in-flow.

One geometry of the flow duct, which is advantageous in application, isthat the flow duct has a nozzle and a downstream diffuser with aspecified opening angle and that the control fluid flow can beintroduced in a transition peripheral region between the nozzle and thediffuser. This configuration of the flow duct geometry permits veryaccurate control of the cooling air flow, which flows first through thenozzle and then through the diffuser, a very small control fluid flow,which is fed into the cooling air flow between the nozzle and thediffuser, being sufficient.

In the case of a radial arrangement of the introduction of the controlfluid flow, as presented above, the control fluid flow is preferablyintroduced in the region of the beginning of the diffuser. Theintroduction of the control fluid flow achieves a non-uniform incidentflow into the diffuser, by which the pressure recovery in the diffuseris reduced. A powerful supply of control fluid achieves almost completedisturbance of the incident flow so that, finally, the pressure recoveryis almost completely prevented. In this way, the flow rate and the massflow through the nozzle become minimal. If the control fluid flow fails,the originally adjusted flow of cooling air flows through the nozzle andthe diffuser.

In the case of a tangential feed of the control fluid flow into thecooling air flow, the control fluid flow is preferably supplied to thecentral region of the nozzle. In this way, the swirl generatedstabilizes the diffuser flow. The pressure recovery and the mass flowthrough the nozzle is increased. Introduction procedures which arelocated between an extreme secant-type inlet flow and a radial inletflow are also possible. This provides less eddying and, in addition, aless powerful swirl, which again exerts and influences on the flow rate.

If the diffuser, through which flow occurs, has an opening angle ofapproximately 10° and there is a ratio of approximately 1:3 between theinlet area of the nozzle and the outlet area of the diffuser, a controlrange of the individual throttling element, which includes nozzle anddiffuser, of 70% to 100% of the undisturbed flow rate can be achieved inthe case of a radial introduction of the control fluid flow. This verywide control range can be adjusted by changing the pressure of thecontrol fluid flow.

If the diffuser, through which flow occurs, has an opening angle ofapproximately 30° and there is a ratio of approximately 1:3 between theinlet area of the nozzle to outlet area of the diffuser, a diffuser isobtained which only generates a trivial pressure recovery. If, in thiscase, the control fluid flow is fed tangentially into the nozzle, thecontrol range of the throttle element consisting of nozzle and diffuserreaches 100% to almost 140% of the unaffected flow rate of the coolingair flow during the control fluid pressure adjustment.

An extension of the control range of the throttle element can beachieved if a plurality of the appliances described above are connectedin series or parallel, the cooling air flowing through the appliances.In this way, for example in the case of a series connection of throttleelements, a cooling air flow reduced in the case of radial incident flowto 70% of the undisturbed flow rate is again reduced in the case of flowthrough the second throttle element, by which it is possible to achievea reduction of the undisturbed flow rate to approximately 50%. If thecontrol flows fail, the originally adjusted undisturbed cooling airflow—as already mentioned above—flows again. A cooling air flow istherefore present in every case of disturbance of the control appliance,which is very advantageous for cooling purposes or other gas controlsfor ensuring a certain basic supply in order to prevent destruction ofinstallations, for example because of a failure of a cooling function.

The control fluid flow can, in particular, be a control gas flow. Evenhot or aggressive gases can be safely controlled by the applianceproposed. Mechanical parts, which could for example be damaged byoxidative or corrosive attack and would, because of this, lose theirfunction, are—in association with the control gas flow—unnecessary forachieving a continuous control of the active gas flow. In order tocontrol a hot active gas flow in the case of a very small control gasflow, it is not absolutely necessary for the control gas flow to havethe same temperature as the active gas. This facilitates the generationand the introduction of the control gas flow because no sort oftemperature measurement has to take place.

In the case of the use of the control appliance in a gas turbine, forexample, both gas flows can also, however, be taken from the same gassource, which is compressed in the gas turbine, it being unnecessary forthem to have the same gas parameters, such as pressure and temperature.

Very good utilization of the advantages, mentioned above, of the controlappliance is possible in a gas turbine. A gas turbine, having rotorblades inserted on carrier disks, having stationary guide bladesarranged between the carrier disks, cooling air flowing through theguide blades from a radially outer region to a radially inner region.The gas turbine further includes, between the respective rotor blade andguide blades, a carrier disk lateral space to which at least part of thecooling air flowing through the guide blade can be supplied. It hasparticularly high requirements with respect to the endurance and thefreedom from maintenance of a throttle appliance for the cooling airemerging into the carrier disk lateral space, as has already been shownin the introduction. There are, in addition, severe effects due to highworking gas temperatures.

With respect to the gas turbine, the object is achieved by at least oneguide blade having, at a radially inner end region, an appliance whichinfluences the cooling air supply to the carrier disk lateral space.

Such a control appliance blocks a supply of air from the hot gas ductfrom entering the carrier disk lateral space, and therefore preventsdamage. This is done by cooling air expelled from the control appliance,air also designated as “blockage air”, and by associated “excesspressure” in the carrier disk lateral space relative to the hot gasduct. By such an appliance, the cooling air supply is controlleddirectly at the radially inner end region of the guide blade during theinward flow of the cooling air into the carrier disk lateral space, andnot previously in the cooling air supply duct to the guide blade. Acontrol arrangement in the cooling air supply duct to the guide bladeinfluences, as shown above, not only the cooling air supply to thecarrier disk lateral space but also the cooling air supply to filmcooling holes at the blade nose which, in the case of very low coolingair pressures, can lead to undesirable film breakdowns and thereforeoverheating of the blade nose. Control at the radially inner end region,which also includes adjacent components of the guide blade, for example,permits the required cooling air quantity to be minimized, which leadsto a higher efficiency of the gas turbine without influencing the gaspressure at the film cooling holes. By the appliance proposed, thecooling air supply can be individually matched to the special geometryof the blades and of the carrier disk lateral spaces.

A particular effectively controllable and low-maintenance appliance forinfluencing the cooling air supply to the carrier disk lateral space ofa gas turbine is provided by a control appliance being attached at theradially inner end region of a guide blade, by which the cooling airsupply to the carrier disk lateral space can be controlled by a controlair flow, as has been presented above in various forms. An embodiment ofthe invention then represents, so to speak, a pneumatic or aerodynamicquantity control of the blockage air.

The magnitude of the cooling air supply to the carrier disk lateralspace does not have to be determined from the outset as soon as theguide blade is installed in the gas turbine, but can be subsequentlyadjusted by the control air flow with respect to the desired flowbehavior at the radially inner end region. This is thereforeparticularly advantageous because, during the manufacturing process, noguide blade appliance corresponds exactly to another one. In this way,the cooling air supply can be optimized and the cooling air requirementcan be minimized retrospectively by easy alterations to the cooling airflow. In this way, excessive cooling air is avoided but, at the sametime, reliable cooling of the carrier disk lateral space is ensured.

An independent and low-maintenance appliance for supplying the coolingair flow to the throttle element at the radially inner end region of aguide blade is provided by it being possible to supply the control airflow through a feed duct to the transition peripheral region between thenozzle and the diffuser, the feed duct being provided within the guideblade and having a control appliance at its outer end region foradjusting the control air pressure. In this way, the control air flow atthe radially inner end region of a guide blade can be adjusted, so tospeak, “by remote control” without complex mechanical appliances beingnecessary for this purpose. The control air flow always keeps its ownsupply free from dirt and therefore permits a long life for thethrottling appliance. The control takes place outside the inner radialend region of the guide blade, which is severely affected by hightemperatures, and is therefore easily accessible for maintenance.

The function of the throttle appliance is, again, not impaired when itis subject to high temperature and it has a permanently high controlrate. It can also be overloaded occasionally without damage, for exampledue to an excessively high pressure adjustment of the control air flow.The air flow then only impinges on the walls of the nozzle or thediffuser but cannot seriously damage them. In the case of failure of thecontrol system, a basic flow of cooling air occurs in any event and thiscan be adjusted independently of the function of the control air flowbefore the gas turbine is put into operation. For example, this can bedone by a predetermined size of the openings in the flow duct and afixed adjustment of the cooling air flow, set in such a way that itsflow is sufficient for the desired function. If the control air flow canbe selected to be very small, the feed duct is also small and cantherefore be easily accommodated within the guide blade. Outside theguide blade, it would interfere with the operation of the gas turbineand make control impossible.

A high level of continuity and a reliable supply of the control air flowcan be ensured by the feed duct having an intermediate region betweenthe control appliance, which is provided in its outer region, and theentry into the transition peripheral region between the nozzle and thediffuser, the intermediate regions being connected by appliances, whichinfluence the cooling air supply, of a plurality of guide blades of acarrier disk. This intermediate region, which represents a type ofreservoir for the control air flow, permits the supply of a constantcontrol air flow even if, sometimes, small fluctuations occur in thesupply of the control air or if the pressure changes. A connectionbetween the intermediate spaces of different guide blades by a type ofsupply duct further stabilizes the control air pressure and, inaddition, permits a reduction in the number of control appliancesnecessary for the control of the control air flow.

In addition, the intermediate region permits cooling of the materialsurrounding it and therefore also serves to reduce the temperature inthe region of the radially inner end region of the guide blades.

BRIEF DESCRIPTION OF THE DRAWINGS

The appliance for and the method of controling the cooling air flow, inparticular a gas turbine cooling air flow, are explained in more detailusing the exemplary embodiments represented in the drawings. In these:

FIG. 1a shows, diagrammatically, an active fluid control appliance inlongitudinal section,

FIG. 1b shows, diagrammatically, a longitudinal section through anexcerpt from a gas turbine,

FIG. 2a shows an enlarged excerpt from FIG. 1b relating to a throttleelement with radial control air supply,

FIG. 2b shows a cross section through a control appliance with radialcontrol air supply,

FIG. 3a shows an enlarged excerpt from FIG. 1b, having a controlappliance with tangential air supply,

FIG. 3b shows a cross section through a control appliance withtangential control air supply as shown in FIG. 3a, and

FIG. 4 shows a longitudinal section through a plurality of guide bladeswith connected control appliances.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1a shows, diagrammatically, not to scale and in principle theconstruction of an active fluid control appliance. The active fluid 1flows through a flow duct 2. The shape of the flow duct 2 is notspecified but is here assumed to be cylindrical. A control fluid duct 34is provided to the side of the flow duct 2 and a control fluid flow 30is supplied to the cooling air flow 1 flowing through the flow duct 2 bythis cooling fluid duct 34. The geometry of the cooling fluid duct 34 islikewise not specified, in particular the transition 45 from the coolingfluid duct 34 to the flow duct 2. Depending on whether it is desired togenerate a laminar or a turbulent flow, it is appropriate to select acorresponding transition 45, for example matched, rounded edges. Thecontrol fluid flow 30 can be resolved into at least two flow components3, one flow component 3 being always provided transverse to the flowdirection 30 of the cooling air flow through the flow duct 2. Thisresolution into flow components 3 should be understood vectorially, inthe resolution one flow component 3 being selected in such a way that itis parallel to the flow direction 35 of the cooling air flow 1 throughthe flow duct 2.

The flow rate of the cooling air flow 1 can be adjusted by the controlfluid flow 30, which is introduced into the cooling air flow 1. Thisoccurs because the flow behavior of the cooling air flow 1 is altered bythe introduction of the control fluid flow 30. Two primary alterationsto the flow rate are fundamentally conceivable, on the one handacceleration of and, on the other, hindrance to the flow of the coolingair by the laterally introduced control fluid flow 30. The strength andtype of the control of the cooling air flow 1 by the control fluid flow30 depends, on the one hand, on the introduction geometry of the controlfluid flow 30 into the cooling air flow 1. By this is to be understood,for example, the transition 45 from the cooling fluid duct 34 to theflow duct 2, for example an arrangement with edges or a roundedarrangement. The angles 17 at the transition 45 between the controlfluid duct 34 and the flow duct 2 can also be altered and, therefore,the direction of the entering control fluid flow 30. The size of thecontrol fluid duct 34, in particular its thickness 36, can also bealtered. Further influence possibilities lie, for example, in theselection of a certain geometry of the flow duct 2. As an example, theflow duct can be selected to be larger or narrower or to have afunnel-shaped outlet opening 25, as is represented in FIGS. 1b, 2 a and3 a. If the arrangement geometries are fixed, the cooling air flow 1 canstill be adjusted as a function of control parameters of the controlfluid flow 30. The adjustment of the pressure of the control fluid flow30 is, in particular, proposed as a control parameter.

Control of the cooling air flow 1 by a control fluid flow 30 ispossible, even with very small flow rates of the control fluid flow 30.In this way, the cooling fluid duct 34 can be kept very small relativeto the flow duct 2 and the overall appliance can also be easilyaccommodated at very inaccessible locations, for example, withinmachines.

FIG. 1b shows, diagrammatically and not to scale, an excerpt from a gasturbine with rotor blades 8 inserted on carrier disks 7 and withstationary guide blades 11 arranged between the carrier disks 7. In thisarrangement, the rotor blades 8 are driven by the hot gas flow 22, thehot gas flow 22 flowing through between the rotor blades 8 and the guideblades 11. In this arrangement, both the rotor blades 8 and the guideblades 11, which are fitted in a stationary manner at the periphery ofthe gas turbine, are subject to the high temperatures of the hot gasflow 22. Although the blades are manufactured from a high-temperatureresistant material, further cooling is frequently necessary.

The cooling of the guide blade 11 represented in FIG. 1b lies in coolingair 1′ from the periphery of the gas turbine being led to the radiallyouter region 9, through the inside of the guide blade 11 as far as aradially inner region 10 of the guide blade 11. The discharge: of thecooling air 1′ essentially takes place at the film cooling holes 28,which generate a cooling film on the outside of the guide blade 11, andalso by a discharge duct in the radially inner region 10 of the guideblade 11, which duct has a nozzle 2′ and a diffuser 3′. In thisarrangement, the emerging cooling air 1′ is guided into a carrier disklateral space 12, which is formed in each case between one rotor blade 8and one guide blade 11. The carrier disk lateral space 12 is essentiallybounded by the side wall 38 of the root 26 of the rotor blade 8, anupper region 27, which is adjacent to the carrier disk 7 and to whichthe root 26 of the rotor blade 8 is fastened, a lower side wall 39 ofthe guide blade 11 and the collar 37 of the rotor blade 8 and the collar40 of the guide blade 11, the collars being sealed relative to oneanother by way of a sealing lip 20. This connection of the two collars37 and 40 separates the hot gas duct 18 for the hot gas flow 22 from thecarrier disk lateral space 12. The hot gas air 22 can, however,partially penetrate into the carrier disk lateral space 12 at thesealing lip 20 and heat the carrier disk lateral space 12 in anundesirable manner; this is prevented by the cooling arrangementproposed.

At its radially inner region 10, the guide blade 11 is provided withtransition seals 24, the end seal 21, in particular, between theradially inner region 10 of the guide blade 11 and the wall 27, which isadjacent to the carrier disk lateral space 12 which is in contact withthe carrier disk 7, separates—from one another—two carrier disk lateralspaces 12 adjacent to the guide blade 11. The cooling air 1′ emergingthrough the nozzle 2′ and the diffuser 3′ is controlled by a controlappliance 23 which feeds, via a feed duct 14 which extends radiallythrough the inside of the guide blade, a control air flow 4 to a widenedintermediate region 15. From this, a duct 16 leads off which introducesthe control air flow 4 supplied into the nozzle 2′, or into the diffuser3′ or into the transition peripheral region 5 between the nozzle 2′ andthe diffuser 3′. The control air flow 4 is controlled by a controlappliance 23, which is preferably located at the upper region of thefeed duct 14. In this way, a control air flow 4, which increases orreduces the flow rate of the cooling air flow 1′, is supplied at varyingflow strength to the cooling air flow 1′ emerging through the nozzle 2′and the diffuser 3′.

The strengthening function occurs particularly when, as shown in FIG. 3aor 3 b, the duct 16 leading away from the widened intermediate region 15is brought in the manner of a secant to the transition peripheral region5, so that a swirl occurs which entrains the cooling air 1′ flowingthrough and, in this way, increases the flow rate. A reduction in theflow rate occurs particularly when, as shown in FIGS. 2a and 2 b, theduct 16 leading away from the intermediate region 15 is insertedradially, i.e. almost centrally therefore, into the region of the nozzle2′, so that the entering control air 4 compresses the through-flowcooling air flow 1′, or reduces its flow rate.

Fixed control ranges of the control appliance can be achieved at acertain, specified ratio between the inlet area 30 of the nozzle 2′ andthe outlet area 25 of the diffuser 3′.

Because of the long and extremely thin feed duct 14, which supplies thecontrol air within the guide blade 11 to the widened intermediate region15, it is also possible, at a more remote control appliance 23, to havean influence on the “remotely controlled” adjustment procedures in thethrottle element 42. In this way, an almost maintenance-free throttleelement is obtained at the radially inner end region 13 of the guideblade 11, which can also include adjacent components, i.e. at a positionin the guide blade 11 which has poor access for conventional control andmaintenance procedures. At the same time, however, an economical use ofthe cooling air 1′ is ensured by the control air flow 4 being easilyadjusted by the control system 23 in such a way that only the preciselyrequired cooling air quantity 1′ flows out through the nozzle 2′ or thediffuser 3′ into the carrier disk lateral space 12, and not anunnecessarily powerful cooling air flow 1. The accurate adjustment alsoprevents breakdown of the film cooling by means of the cooling air 1′flowing through the film cooling holes 28.

FIG. 4 shows a longitudinal section through a plurality of controlappliances, of adjacent guide blades 11, connected by a widenedintermediate region 15. In this arrangement, the control air flow 4 iscontrolled by a control system 23 for a plurality of guide blades 11; aplurality of control systems 23 can also, however, be applied.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. An apparatus for controlling a cooling air flowwhich flows through a flow duct of a gas turbine, comprising: a controlfluid flow channel, including a control fluid flow introduced into theflow duct, with a flow component transverse to the flow direction of thecooling air flow through the flow duct, wherein a flow rate of thecooling air flow is influenced as a function of the control fluid flow,said control fluid flow being dynamically variable.
 2. The apparatus asclaimed in claim 1, wherein the flow rate of the cooling air flow isadjustable as a function of control parameters of the control fluidflow.
 3. The apparatus as claimed in claim 2, wherein the flow rate ofthe cooling air flow is adjustable by adjusting the pressure of thecontrol fluid flow.
 4. The apparatus as claimed in claim 1, wherein theflow rate of the cooling air flow is adjustable by adjusting thepressure of the control fluid flow.
 5. The apparatus as claimed in claim1, wherein the flow rate of the control fluid flow is small relative tothe flow rate of the cooling air flow.
 6. The apparatus as claimed inclaim 1, wherein the control fluid flow is radially introducable intothe cooling air flow flowing through the flow duct.
 7. The apparatus asclaimed in claim 1, wherein the control fluid flow is tangentiallyintroducable into the cooling air flow flowing through the flow duct. 8.The apparatus as claimed in claim 1, wherein the control fluid flow isintroducable in the manner of a secant into the cooling air flow flowingthrough the flow duct.
 9. The apparatus as claimed in claim 1, whereinthe flow duct includes a nozzle and a downstream diffuser with aspecified opening angle, and wherein the control fluid flow isintroducable in a transitional peripheral region between the nozzle andthe diffuser.
 10. The apparatus as claimed in claim 9, wherein thediffuser, through which flow occurs, includes an opening angle ofapproximately 30° and wherein there is a ratio of approximately 1:3between an inlet area of the nozzle and an outlet area of the diffuser.11. The apparatus as claimed in claim 9, wherein the diffuser, throughwhich flow occurs, includes an opening angle of approximately 10° andwherein there is a ratio of approximately 1:3 between an inlet area ofthe nozzle and an outlet area of the diffuser.
 12. The apparatus asclaimed in claim 1, comprising: a plurality of apparatuses connected inseries or parallel, with the cooling air flow flowing through theapparatuses.
 13. The apparatus as claimed in claim 1, wherein thecooling air flow is an effective gas flow and the control fluid flow isa control gas flow.
 14. The apparatus as claimed in claim 1, wherein theflow of the cooling air is further influenced by an angle of the controlfluid flow channel with respect to the flow duct.
 15. The apparatus asclaimed in claim 1, wherein the flow of the cooling air is furtherinfluenced by the shape of the flow duct.
 16. The apparatus as claimedin claim 1, wherein the flow of the cooling air is further influenced byan angle of the control fluid flow channel with respect to the flow ductand the shape of the flow duct.
 17. A gas turbine comprising: rotorblades inserted in carrier disks; stationary guide blades arrangedbetween the carrier disks, wherein cooling air flows through the guideblades from a radially outer region to a radially inner region; andbetween the rotor blades and the guide blades, a respective carrier disklateral space to which at least part of the cooling air flowing throughthe guide blades is supplied, wherein at least one guide blade includes,on a radially inner end region, an apparatus which influences coolingair supply, said apparatus including a control fluid flow channelpermitting control fluid to influence the cooling air flow, said controlfluid flow being dynamically variable.
 18. The gas turbine as claimed inclaim 17, wherein an apparatus influencing cooling air supply isprovided at the radially inner end region of said at least one guideblade, by which the cooling air supply to the carrier disk lateral spaceis controllable by a control air flow.
 19. The gas turbine as claimed inclaim 18, wherein the control air flow is supplyable through a feed ductto the transition peripheral region between the nozzle and the diffuser,the feed duct being provided within the guide blade and including acontrol apparatus in its outer region for adjusting the control airpressure.
 20. The gas turbine as claimed in claim 17, wherein thecontrol air flow is suppliable through a feed duct to the transitionperipheral region between the nozzle and the diffuser, the feed ductbeing provided within the said at least one guide blade and including acontrol apparatus in its outer region for adjusting the control airpressure.
 21. The gas turbine as claimed in claim 17, wherein the feedduct includes an intermediate region between the control apparatus,provided in its outer region, and its entry into the transitionalperipheral region between the nozzle and the diffuser, the intermediateregions being connected by more than one apparatuses, which influencethe cooling air supply, of the guide blades of the carrier disks. 22.The gas turbine as claimed in claim 17,wherein the flow of the coolingair is further influenced by an angle of the control fluid flow channelwith respect to the flow duct.
 23. The gas turbine as claimed in claim17, wherein the flow of the cooling air is further influenced by theshape of the flow duct.
 24. The gas turbine as claimed in claim 17,wherein the flow of the cooling air is further influenced by an angle ofthe control fluid flow channel with respect to the flow duct and theshape of the flow duct.
 25. A method of controlling a cooling air flowwhich flows through a flow duct comprising: introducing a control fluidflow into the cooling air flow, in the region of the flow duct, with aflow component transverse to the flow direction of the cooling air flowthrough the flow duct; and adjusting the flow rate of the cooling airflow as a function of the control fluid flow, said control fluid flowbeing dynamically adjustable.
 26. The method as claimed in claim 25,wherein the flow rate of the cooling air flow is adjusted as a functionof control parameters of the control fluid flow.
 27. The method asclaimed in claim 26, wherein the flow rate of the cooling air flow isadjusted by adjusting the pressure of the control fluid flow.
 28. Themethod as claimed in claim 25, wherein the flow rate of the cooling airflow is adjusted by adjusting the pressure of the control fluid flow.29. The method as claimed in claim 25, wherein the flow rate of thecontrol fluid flow is small relative to the flow rate of the cooling airflow.
 30. The method as claimed in claim 25, wherein the control fluidflow is introduced radially into the cooling air flow flowing throughthe flow duct.
 31. The method as claimed in claim 25, wherein thecontrol fluid flow is introduced tangentially into the cooling air flowflowing through the flow duct.
 32. The method as claimed in claim 25,wherein the control fluid flow is introduced in the manner of a secantinto the cooling air flow flowing through the flow duct.
 33. The methodas claimed in claim 25, wherein the cooling air flow flows through anozzle and a downstream diffuser with a specified opening angle, and thecontrol fluid flow is introduced in a transitional peripheral regionbetween the nozzle and the diffuser.
 34. The method as claimed in claim33, wherein the diffuser, through which flow occurs, includes an openingangle of approximately 30°, and wherein there is a ratio ofapproximately 1:3 between an inlet area of the nozzle and an outlet areaof the diffuser.
 35. The method as claimed in claim 33, wherein thediffuser, through which flow occurs, includes an opening angle ofapproximately 10°, and wherein there is a ratio of approximately 1:3between an inlet area of the nozzle and an outlet area of the diffuser.36. The method as claimed in claim 25, wherein the cooling air flow iscontrolled by a plurality of apparatuses connected in series orparallel.
 37. The method as claimed in claim 25, wherein the cooling airflow is an effective gas flow and the control fluid flow is a controlgas flow.
 38. The method as claimed in claim 25, wherein the flow of thecooling air is further influenced by an angle of the control fluid flowchannel with respect to the flow duct.
 39. The method as claimed inclaim 25, wherein the flow of the cooling air is further influenced bythe shape of the flow duct.
 40. The method as claimed in claim 25,wherein the flow of the cooling air is further influenced by an angle ofthe control fluid flow channel with respect to the flow duct and theshape of the flow duct.